Telephone apparatus generally can be connected to subscribers and terminal devices. Large private telecommunications installations may reach in excess of 1000 subscribers. If these telecommunications installations are networked, for example through QSIG, communications systems can result in numbers of subscribers which are only limited by the maximum permissible length of the calling number used to indicate the subscriber or the device which is calling or to be called.
Telecommunications installations of this magnitude not only require a broad spectrum communications path, but employ features which are not obtainable with smaller telecommunication systems and can, for example, also allow server based applications like CTI (Computer Telephony Integration), CRM (Customer Relations Management) and Call Center Technology.
The performance features of telephone installations are capable of implementation at different costs. Complex communications technologies and server based applications are relatively expensive to provide because of the capital cost and thus are often uneconomical for small numbers of communications. Features which require advanced technology thus cannot be provided in small telephone installations. Features of that type however may be available for larger telecommunication installations with many clients which each may have many substantial groups, in which case the cost of any performance feature per subscriber may lie in a more economical range.
Two known approaches of this type is Centrex service utilizing a public network of Deutschen Telekom AG in Germany and the “multicompany” approach provided by private telecommunications suppliers. The Centrex service can provide private telephone installations connected to the open net centrally for many clients. The service uses both characteristics of private telephone systems and characteristics of the open net. The network intelligence, i.e. the control for the features, takes place through the open net and the interface between the open net and the private network is a virtual location with the function of a gateway between the nets.
The multicompany approach is based upon private network principles and uses telephone installations at each individual location. In a large apparatus, the communication system of the building or the plant is operated through a network driver of the type supplied by AVAYA TENOVIS or by Regus Corporation, U.K. The network intelligence is located in the primary network on the campus and the transition to the open network Os likewise a campus. The private network can include a plurality of private telephone installations.
A number of legally distinct and independent clients or customers can be provided for each telephone installation. An administrator operates the network driver of the installations and implements the performance features selected by the client and makes available the communication for the subscribers of the company. The private telephone installations known in the art are not designed for such applications and it has not been possible heretofore to provide simultaneously and individually all possible combinations of performance features for all of the individual customers or clients. As a consequence, the operator of campus networks generally provides packages of performance features which can be simultaneously applied.
In one existing system, the number of firms serviced is limited to 64 and the telephone apparatus cannot recognize the firms or customers or clients. The result is a limitation in the handling of communications with clients, substituting the formation of traffic groups for a client recognition.
It is common to refer to the “client” and “customer” in connection with the supply of telephone services and to refer to such parties each as having a number of subscribers, each of which represents a terminal device. The term “subscriber” is used to represent the terminal device as well and the subscriber identification number is likewise that of the device. With the aid of call number plans the relationship between subscriber lines to the terminal device and the internal call number of the subscriber can be established.
It is also known to provide a telecommunication system with an exchange which can include a telecommunication apparatus or installation. The exchange is usually capable, through digital communications, to connect that apparatus to other telecommunication apparatuses each with their respective central or exchange. For convenience, the term “central” may be used herein to refer to the telephone connection apparatus to which the subscriber lines are connected in a particular local system and that apparatus may also be referred to as the central. The communications protocol used may be either a standardized protocol (QSIG, DPNSS1) or a proprietary protocol (TNET, CORNET, . . . ). Telecommunication apparatus in an exchange can have devices which can charge for the use of the line per connection, and for connection duration. The art also is aware of an exchange of private telecommunication apparatus all of which are associated with a particular client.
Conventional systems which are customer based and are in the field of private communication apparatuses have been limited in many cases by the fact that the particular telecommunication apparatus is limited to a single customer or client. While it is true that the apparatus can be connected via an exchange with other telecommunications apparatus, in general in the past such private telecommunication apparatuses have not been capable of serving large numbers of clients and subscribers or terminal devices of a number of clients could not be conveniently accessed through many private telecommunication apparatuses. This is especially disadvantageous because communications between terminal devices of the same client are treated differently in connections between terminal devices of different clients. Many firms have geographically widely distributed subsidiaries or enterprise that in the past have been treated as different clients and may have calling number plans which may overlap in assignment of numbers. As a consequence, communication between them has been complicated in a private telephone system.
Private telephone systems by comparison to communications over open networks, may have a calling number plan in which calling numbers internal to the apparatus are assigned to the respective terminal devices. Such calling number plans are apparatus specific and thus the internal calling number is in general limited to that apparatus. It is possible to coordinate the calling number plans of a plurality of apparatuses with the drawback that with increasing number of subscribers in a coordinated system usually more digits are required to indicate each terminal device than would otherwise be required. Usually these calling number plans do not provide any recognition of the particular apparatus or its access line.
A client calling number plan of a customer based telecommunication apparatus must generally be capable of extending beyond a particular geographic region even though each particular region may be associated with a region code. In the case of a private communication system this can be a drawback when a client already has separate telecommunication apparatuses at different locations and each location has its own calling number plan. For that particular client it is not uncommon that at various locations the same calling number will be used. If these locations are to be connected to a central, the calling number plans must be revised so that the terminal devices again become singularly determined by their internal calling numbers.